Treatment of HSV-1 infection with immunoglobulin or acyclovir: Comparison of their effects on viral spread, latency, and reactivation

We compared immunoglobulin (IgG) and acyclovir (ACV) therapies on the establishment, maintenance, and reactivation from latency of HSV-1(McKrae) in a mouse ocular infection model. Mice were given one intraperitoneal (IP) dose of human IgG 24 h after infection (Day 1 p,i.) or ACV in the drinking water from Days 1 to 7 p.i. Both treatments allowed similar percentages of mice to survive the infection and decreased ocular virus shedding as compared with untreated controls. At most time points, there were no differences between IgG- and ACV-treated animals with respect to tissue virus titers or in the rates of virus reactivation during explant cocultivation. However, after ultraviolet exposure, HSV reactivated in 30% of ACV-treated mice compared with 90% of IgG-treated mice (P = 0.02). Also by quantitative PCR, we found more latent HSV-1 DNA copies in IgG-treated mice compared with those given ACV (P = 0.02). IgG treatment protects mice from HSV-1 infection essentially as well as ACV does. Nonetheless, it permits higher levels of latent infection and subsequent in vivo reactivation. These studies have implications for the mechanism by which IgG functions to attenuate HSV infections and for its potential value as a therapeutic agent in humans.